Enter RQPJZZOU (bonus code 9535).
Glitch: Drive any car on any track on Xbox Live:
Create an Xbox Live session. Enter the "Settings" menu then choose
the series with the car you wish to drive. Press A to select the
series, then select "Continue". Re-enter the "Settings" menu. Now,
choose the series with the tracks you wish to drive. Press A to
select the series. However, instead of selecting "Continue", return
to the series selection screen. Choose the 1st series that you
selected, then press A. Select "Continue", go to "Track", then press
X at the "Reset Championship" option. Go to the "Track" option, then
choose the desired track.

Use the following trick to change your bonus code. For example, if
you want to use the cheats for "9535" but your number is different.
Delete your game file from your hard drive, then reload the game.
You will have a new bonus code. Repeat this process until you get
the desired number.